I'm mostly curious about if troll biology is ever like really explained. Like do they need to sleep and eat and where do they come from. If Gunnar was born from the heart stone how do they have kids? And I heard there are books have you read them?
I’m not expert but I will try to answer your questions. Unfortunately, troll biology is sadly not too expounded upon. From the show, such things aren’t really talked about. The comics and books address a little of it, but those aren’t really canon-canon per say, since there are inconsistencies between them. Still, you might find them useful.
(Trollhunters comic: The Secret History of Trollkind) for eating and sleeping, this comic seems to show they do get hungry and need sleep, though it is theorized that this is because they are without the heartstone for sustenance.
The ability to have kids part is still debatable. The show shows many trolls with female and male phenotypes and use the words gronk-nuks in place of nut-sack. However, in the book Trollhunters: The Way of the Wizard, Draal is supposedly born from a rock egg thing of some sort that his parents made together by taking stones off their body I think? So it appears that some trolls that are born of stone.
Anyways, here’s a list if you’re interested in learning more. I would suggest finishing the show before reading the The Felled or some of the other books. There’s some spoilers in them:
1. Trollhunters: The History of Trollkind
2. Trollhunters: The Felled
Companion Books to the show:
1. Trollhunters: The Adventure Begins (First two episodes in written form)
2. Trollhunters: Journey to the Darklands (Story between the end of the first season and the beginning of the second)
3. Trollhunters: The Book of Ga-Huel (Set in Season 2. Blinky gets a hit on him and there’s a polymorph on the loose)
4. Trollhunters: Age of the Amulet (The Trollhunters go back in time. I’m not joking. It’s a Bill and Ted Adventure.)
5. Trollhunters: Way of the Wizard (Season 3 spoilers. It’s got Merlin in it).
I hope that somewhat answered your question. Anyone else is welcome to add to this post.